Exemplary embodiments relate to a nonvolatile memory device and a method of manufacturing the same and, more particularly, to a nonvolatile memory device and a method of manufacturing the same, which are capable of improving passage of current from a signal line to a string structure.
NAND flash memory devices, a type of nonvolatile memory device facilitating higher capacity and higher degree of integration, have been actively developed. The memory cell array of the NAND flash memory device includes string structures arranged in a matrix form. Each of the string structures includes a drain select transistor having a drain coupled to a bit line, a source select transistor having a source coupled to a common source line, and a number of memory cells coupled in series. In the string structure, a number of the memory cells are coupled in series between the drain select transistor and the source select transistor. Meanwhile, neighboring string structures can be coupled together through the drain of the drain select transistor or the source of the source select transistor.
More particularly, a semiconductor substrate includes an isolation layers and active regions. The isolation layers and the active regions are alternately arranged in parallel in the memory cell array region. The string structures arranged in a row within one active region are coupled together through the source or the drain formed in the active region of the semiconductor substrate. For example, from among first to third string structures arranged in a row within one active region, the first and second string structures neighboring each other are coupled together through the drain of the drain select transistor. Furthermore, the second and third string structures neighboring each other are coupled together through the source of the source select transistor.
Meanwhile, the string structure is supplied with a drive signal through a signal line formed over an insulating layer. Here, a contact plug, coupled to the drain or the source, is formed in the insulating layer between the signal line and the string structure. Thus, the signal line formed over the insulating layer is electrically coupled to the string structure via the contact plug coupled to the drain or the source. For example, in the case in which the signal line is the bit line of a NAND flash memory device, the bit line is electrically coupled to the string structure via the contact plug coupled to the drain.
As described above, the signal line functions to supply an electrical signal to the string structure via the contact plug coupled to the source or the drain. In order to smoothly transfer current to the string structure, the source or the drain must be stably formed. However, the source or the drain can be lost in a process of manufacturing a nonvolatile memory device. Accordingly, there is a problem in that error is generated in the operations of the nonvolatile memory device because current is not smoothly transferred to the string structure.